Cancer is one of the major causes of death in the world. According to the report from the WHO Fact Sheet-Cancer (2003), cancer accounts for 7.1 million (12.6% of the global total) deaths annually and new cancer cases are expected to be increased from 10 million people in 2000 to 15 million people by 2020. In recent years, much progress has been made toward understanding the molecular and cellular biology of cancers. Many important contributions have been made by the identification of several key genetic factors associated with cancers. However, the treatments of cancers still mainly depend on surgery, chemotherapy and radiotherapy because the molecular mechanisms underlying the pathogenesis of cancers remain largely unclear.
It is interesting to note that receptor tyrosine kinases are a family of proteins reported to be involved in many fundamental cellular processes such as cell cycle, signalling transduction, proliferation, differentiation, adhesion, migration, and apoptosis. An important role of the receptor tyrosine kinases in the development of cancers has been reported previously. Therefore, future strategies for the prevention and treatment of cancers may be focused on the elucidation of the receptor tyrosine kinases which are involved in the pathogenesis of cancers. Ron, a member of the receptor tyrosine kinase family located on human chromosome 3p21 (a region frequently deleted in small cell lung carcinoma), was isolated and identified through the screening of cDNA libraries. Previous studies have indicated that Ron is involved in many genetic mechanisms of the tumor cells (Wang et al., (2003) Carcinogenesis 24:1291-300; Angeloni et al., (2004) J Biol. Chem. 279:3726-32; Peace et al., (2005) Cancer Res. 65:1285-93; Camp et al., (2005) Ann Surg Oncol. 12:273-81), and that Ron is a potential target for understanding the pathogenesis of cancers. In addition, the association between gene variants and diseases has been reported previously. Therefore, the discovery of gene variants of Ron may be important for the diagnostic markers of cancers.